title: Multipathway sequences for MR thermometry.
abstract: MR-based thermometry is a valuable adjunct to thermal ablation therapies as it helps to determine when lethal doses are reached at the target and whether surrounding tissues are safe from damage. When the targeted lesion is mobile, MR data can further be used for motion-tracking purposes. The present work introduces pulse sequence modifications that enable significant improvements in terms of both temperature-to-noise-ratio properties and target-tracking abilities. Instead of sampling a single magnetization pathway as in typical MR thermometry sequences, the pulse-sequence design introduced here involves sampling at least one additional pathway. Image reconstruction changes associated with the proposed sampling scheme are also described. The method was implemented on two commonly used MR thermometry sequences: the gradient-echo and the interleaved echo-planar imaging sequences. Data from the extra pathway enabled temperature-to-noise-ratio improvements by up to 35%, without increasing scan time. Potentially of greater significance is that the sampled pathways featured very different contrast for blood vessels, facilitating their detection and use as internal landmarks for tracking purposes. Through improved temperature-to-noise-ratio and lesion-tracking abilities, the proposed pulse-sequence design may facilitate the use of MR-monitored thermal ablations as an effective treatment option even in mobile organs such as the liver and kidneys.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. bruno@bwh.harvard.edu
authors.forename: Bruno
authors.initials: B
authors.lastname: Madore
authors.forename: Lawrence P
authors.initials: LP
authors.lastname: Panych
authors.forename: Chang-Sheng
authors.initials: CS
authors.lastname: Mei
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Renxin
authors.initials: R
authors.lastname: Chu
mesh_terms: D017115:Catheter Ablation / Q000379:methods*; D003198:Computer Simulation; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000098:blood supply / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D023421:Models, Animal; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012119:Respiration; D013817:Thermography / Q000379:methods*; D013997:Time Factors